Capacitance detection circuit and electronic device
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Solution Overview
Problem
Touch screens with ultra-thin protective layers face challenges in mutual-capacitance sensing due to increased coupling capacitance and baseline current between electrodes and the ground terminal, which reduces the accuracy of touch determination by limiting the dynamic range of the analog-to-digital converter.
Innovation Solution
A capacitance detection circuit is designed with a driving circuit that keeps at least one transmit electrode floating, generating driving signals to compensate the baseline current between receive electrodes and the ground terminal, utilizing driving units and a control unit to manage the conduction states and signal generation, thereby reducing the impact of baseline current on sense results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mutual-capacitance sensing is used in touch screens with ultra-thin protective layers, then the coupling capacitance between electrode and finger increases, but the baseline current between receive electrode and ground terminal increases, reducing measurement precision
Solution Approach 1:
The patent applies preliminary anti-action by generating a compensation signal before the baseline current affects the measurement. The driving circuit generates a compensation signal that is applied to the receive electrode to counteract the baseline current in advance, preventing its harmful effect on the capacitance measurement between transmit and receive electrodes
Solution Approach 2:
The patent introduces a compensation signal as an intermediary element. This compensation signal acts as a mediator between the baseline current and the capacitance measurement, canceling out the baseline current's effect and allowing accurate touch detection without being affected by the harmful baseline current
2Measurement precision
If baseline current flows through receive electrode and ground terminal, then the dynamic range of analog-to-digital converter cannot be effectively utilized, but the accuracy of touch determination is reduced
Solution Approach 1:
The driving circuit generates a compensation signal in advance that counteracts the baseline current before it consumes the dynamic range of the ADC. This preliminary anti-action ensures that the full dynamic range of the analog-to-digital converter is available for detecting actual touch signals, maximizing measurement precision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively utilizes the dynamic range of the analog-to-digital converter, enhancing the accuracy of touch determination by compensating and reducing the baseline current's effect on sense results.
Implementation Method 1
capacitance detection circuit and an electronic device capable of reducing a baseline current between an electrode and a ground terminal... capacitance between a plurality of transmit electrodes and the plurality of receive electrodes... compensate a baseline current between the plurality of receive electrodes and a ground terminal
Data Source
AI summary
The present disclosure provides a capacitance detection circuit, which includes a sense circuit coupled to a plurality of receive electrodes and configured to generate a plurality of sense results, the plurality of sense results being associated with capacitance between a plurality of transmit electrodes and the plurality of receive electrodes; and a first driving circuit coupled to the plurality of transmit electrodes; wherein when the first driving circuit keeps at least one first transmit electrode of the plurality of transmit electrodes floating, the first driving circuit generates at least one first driving signal and sends the least one first driving signal to at least one second transmit electrode of the plurality of transmit electrodes, to compensate a baseline current between the plurality of receive electrodes and a ground terminal.